The present invention relates to a transducer mounted to a spindle. More particularly, the present invention relates to a telemetry system that transmits signals from the rotating transducer to a stationary body.
A common system for transmitting signals from a rotating transducer to a stationary member is by using a contacting slip ring. In vehicle spindle mounted applications, the slip ring, as well as an optional angular encoder, require an anti-rotate connection to a non-spinning portion of the vehicle. Most slip rings also require that the slip ring tracks and brushes be located on a small radius around the axis of rotation for the purposes of decreasing the surface speed of the brushes in the slip ring assembly. Typically, this requires that the slip ring assembly be placed outboard of the vehicle wheel assembly on the axis of rotation. The antirotate connection wraps around the outside of the wheel assembly to attach on the inside of the wheel at the suspension such that the antirotate is attached to a non-rotating portion of the vehicle that follows the wheel steering and bounce so as to avoid relative motion of the vehicle mounting location and the slip ring mounting at the spindle. Accordingly, the slip ring assembly thus projects outwardly from the wheel, which is undesirable since the projection may contact obstacles. In many jurisdictions, local street laws may prohibit driving on public roads with such a projection.
As an alternative to a slip ring, telemetry allows signals from a rotating body to be transmitted wirelessly to a stationary body. Telemetry can have some advantages over slip rings in that it does not rely on a brush contact to transmit the signal. Although telemetry has been incorporated into other vehicle spindle applications, such systems have had many separate components and which are positioned on the rotating and non-rotating portions of the vehicle spindle. In these other assemblies, the spindle bearings provide the means or positioning for components rotating relative to each other. This design may require electrical components to be potted into custom rims. The custom rims are expensive and require alignment of a stationary pick-up device during installation. In addition, the runout of a rim and/or spindle bearings, and/or deformation of the rim under loading can create problems and interferences between the rotating rim components, and the stationary suspension or vehicle mounted components due to varying gap between the stationary body and the rotating body.
In another telemetry system, the telemetry assembly is comprised of a rotor and stator portion, which must be placed on the axis of rotation to maintain low bearing and/or seal speeds and use of standard off the shelf encoder products. Due to the existing vehicle spindle geometry, which occupies the space at the axis of rotation, the telemetry assembly must be placed outboard of the wheel on the axis of rotation. An anti-rotate device must again wrap around the wheel to an attachment point behind the wheel, thereby having the disadvantages discussed above with the slip ring assembly. In addition, these systems are not easily adapted to other wheels or environments.
Accordingly, there is an on-going need to improve telemetry systems in rotating applications such as vehicle spindle or helicopter spindle blade applications. A telemetry system that addresses one or more of these problems would be a valuable design improvement to the current state of the technology.